The objective of this project is to evaluate the capabilities of various tissue lipases and esterases as early mediators in the interactions of animals with xenobiotics containing ester linkages. The major lipase catalyzing hydrolysis of phthalate esters, herbicide esters (e.g. 2,4-D esters) etc. has been isolated from rat pancreas and characterized chemically and mechanistically. Efforts are under way to procure sufficient purified enzyme for use in studies of protein-ligand interactions. BIBLIOGRAPHIC REFERENCES: Albro, P.W., Corbett, B.J. and Latimer, A.D.: Purification and Partial Characterization of Nonspecfic Lipase from Rat Pancreas. Biochim. Biophys. Acta 424: 351-365, 1976. Albro, P.W., Corbett, B.J. and Hass, J.R.: The mechanism for Nonspecific Lipase from Rat Pancreas. Biochim. Biophys. Acta 431: 493-506, 1976.